1. Field of the Invention
The present invention relates to a diopter adjusting device which can be incorporated in a viewfinder of a camera to allow the user to match the viewfinder image to his/her eyesight.
2. Description of the Related Art
Various types of diopter adjusting devices which can be incorporated in a viewfinder of a camera has been proposed. There have been demands for such diopter adjusting devices which are much smaller than conventional ones and which can be easily assembled with a small number of components.
An object of the present invention is to provide a simple and compact diopter adjusting device.
To achieve the objects mentioned above, according to an aspect of the present invention, a diopter adjusting device is provided, including a diopter adjusting lens which is guided in an optical axis thereof; a cam member which is provided rotatable about an axis which is parallel to the optical axis of the diopter adjusting lens, the cam member being provided with a cam surface on an end surface thereof; a motion-transmission lever which is rotatable about a lever axis, the lever axis being positioned between the diopter adjusting lens and the motion-transmission lever and lying on a plane normal to the optical axis; a cam follower portion and an engaging portion formed on one and the other ends of the motion-transmission lever to be engaged with the cam surface and the diopter adjusting lens, respectively; and a spring for constantly bringing the cam follower portion into contact with the cam surface.
Preferably, the spring is a torsion spring having a coil spring portion, the coil spring portion being positioned about the axis of the motion-transmission lever.
Preferably, the motion-transmission lever includes a rocking lever portion having the cam follower portion and the engaging portion, a rotational center portion which extends from a middle portion of the rocking lever portion in a direction parallel to the lever axis, and first and second connecting portions, formed at one and the other ends of the rotational center portion, to be pivoted about the lever axis, respectively.
Preferably, the diopter adjusting lens includes a follower pin which projects in a direction perpendicular to the optical axis of the diopter adjusting lens, wherein the engaging portion of the motion-transmission lever holds the follower pin. Preferably, the engaging portion is bifurcated.
Preferably, a distance from the lever axis to the engaging portion is longer than a distance from the lever axis to the cam follower portion.
Preferably, the diopter adjusting device further includes a lens guide frame in which the diopter adjusting lens is positioned. The diopter adjusting lens includes a plurality of parallel guide legs which extend parallel to each other in a direction of the optical axis of the diopter adjusting lens. The lens guide frame includes a corresponding plurality of linear guide slots in which the plurality of parallel guide legs are respectively engaged to be slidable in the direction of the optical axis of the diopter adjusting lens. Preferably, the follower pin projects from one of the plurality of parallel guide legs.
According to another aspect of the present invention, a viewfinder is provided having a diopter adjusting device. The diopter adjusting device includes a diopter adjusting lens guided along an optical axis thereof, and serving as a rearmost lens element of an eyepiece optical system of the viewfinder; a cam member which is rotatable about an axis parallel to the optical axis of the diopter adjusting lens, the cam member including a cam surface; a motion-transmission lever which is rotatable about a lever axis, the motion-transmission lever being associated with the diopter adjusting lens and the cam member to transmit motion of the cam member to the diopter adjusting lens, wherein the lever axis is positioned between the diopter adjusting lens and the motion-transmission lever and lies on a plane extending perpendicular to the optical axis; a cam follower portion formed on an end of the motion-transmission lever to be engaged with the cam surface; an engaging portion formed on the other end of the motion-transmission lever to be engaged with the diopter adjusting lens; and a spring for constantly bringing the cam follower portion into contact with the cam surface.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2000-181385 (filed on Jun. 16, 2000) is expressly incorporated herein by reference in its entirety.